The invention concerns a device for continuous separation of blanks for book cover material, covers for brochures or similar bendable sheets of a stack of sheets. A stack of sheets is disposed in a magazine in which a conveyor belt supports the stack of sheets. The device feeds the lowest of the stack of sheets periodically from the magazine, the device uses a high friction (skid-proof) surface and openings through which air is sucked, with a suction element grasping the lowest sheet and lifting it from the stack of sheets. The device also includes a blower device for creating an air cushion between the lifted sheet and the sheet next to the bottom sheet of the stack of sheets. The device also includes a removal conveyor system for receiving and further transporting successive sheets as they are removed from the bottom of the stack of sheets.
Patent Application DE 196 16 047 having the same assignee as the present application concerns a device for separating folded sheets for collecting machines, with a magazine for receiving a stack of folded sheets, from which the respectively lowest folded sheet is fed from a time-controlled conveyor belt with a non-skid surface and openings capable of being acted upon by air suction, and grasping the folded sheets in the front area of the folded edge. The width of the conveyor belt forming the bottom of the magazine is reduced with respect to the width of the magazine, so that the rear area of the folded sheets projects over the conveyor belt. The folded sheet is tipped over a suction element grasping the lowest folded sheet in the forward open folded edge area, and creates an air cushion intermediate the lowest folded sheet and the second lowest folded sheet, in order to separate the lowest folded sheet. The air blower can be inserted into the opening slot thus formed so that, on the one hand, separating air is brought onto the sliding plane of the folded sheets, and on the other hand the stacked folded sheets are supported in the rear area projecting over the conveyor belt. A conveyor system in the form of delivery rollers and counter-pressure rollers for receiving and removing the folded sheets fed by the conveyor belt from the stack of folded sheets is located after the conveyor belt.
The task of the invention consists in creating a device for separating blanks for book cover material, envelopes for brochures or similar bendable sheets of a stack of sheets from a magazine of the usual design, which makes a reliable separation of large-format flexible sheets possible. In addition, the arrangement for adjusting the middle of the length of the sheets should be suited as a reference midline.
The task is solved by the apparatus in accordance with claim 1 of this application. Further advantageous embodiments are indicated in the other claims.
An air cushion between the lowest and second-lowest sheet can be intentionally created over the indentation, in the edge area of the sheet to be separated, opened toward the edge of the sheet. By blowing air into this limited area an uncontrolled deviation of blown air is avoided and only a relatively small amount of air is required. The sheets are located with their edge area in a fixed position, so that even materials with a low inherent rigidity are grasped reliably by the suction element. As a result of the indentation the lowest sheet is released from the stack of sheets and at the same time a relative displacement directed inward to the following sheet takes place, by means of which the so-called suction plate effect is avoided. The suction element gets by with a low suction force, which excludes the danger of sucking through and thus double removal.